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Successful startup of agro-industrial biogas plant, Spain

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By JaapK

In August and September 2017 Coltrade B.V. and its partner Ahidra S.L. have started up one of the largest organic waste to energy recovery facilities in the world which is operating within the agro industry. After 1½ year of dedicated building and construction activities, the plant is currently being started up. The installation is located in Asturias (northern Spain). After full commissioning (Q2/3 2018) the plant will generate 4.5 MWe from an organic waste stream at an average of 1.100 ton per day which consists mainly of cow-manure. These characteristics make it one of the world largest agro-industrial biogas plants!

The waste menu primarily consists of cow manure and is enriched with a variety of co-substrates, which makes the plant capable of accepting waste streams from different agricultural activities and economic sectors. It is a complicated project, tackling a wide variety of environmental issues thanks to the portfolio of technological and technical know-how from Coltrade & Ahidra. Creativity and motivation to succeed were combined to overcome complicated challenges during the construction and startup phase. Finally this project represents a world class showcase of how to comprehensively manage and mine cow manure.

The biogas plant processes mainly cow-manure to produce biogas. To boost biogas production, vegetables and whey are added as co-digestibles. Biogas production takes place in 4 large digesters of ca. 7,000 m³ each. The digesters are operated in thermophilic mode (52˚C) under continuous agitation and heating by 3 DigestMix® systems per digester. The biogas produced is desulphurized and purified by a BIDOX® installation before it is processed via co-generation in the CHP’s thus producing up to 4.5 MW of electricity and heat on a daily basis. By mid November 2017 the plant is already producing 300 m³ of biogas per hour.

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Panoramic view of the construction (click to enlarge)

The digestate resulting from the digesters is separated in a liquid and a solid fraction by means of a decanter centrifuge. The solids (digestate cake) is further dried using the excess co-generation heat before it can be used as a fertilizer. The liquid fraction from the decanter centrifuge is further treated in an aerobic SBR-NAS® system equipped with an MBR, to purify the effluent before it can be discharged. The aerobic system effectively removes nitrogen and COD and the effluent is free of suspended solids. In order to produce an effluent that qualifies for discharge towards open water (the nearby sea), the residual phosphorus is recuperated in a final purification step via struvite precipitation by an ANPHOS® installation.

Once more Coltrade & Ahidra have realized a superb integrated solution to world climate threatening environmental problems. In this case the technology and know-how is applied to valorize highly complex waste into energy, nutrient recovery into bio-fertilizers and clean effluent that meets stringent permit requirements.

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